Annealing furnace



Aug. 23, 1949. c. CONE I 2,479,814

' ANNEALING FURNACE Filed Dec. 22, 1945 g Maw; $41M Patented Aug. 23,1949 2,473,814 smmauno runmca CarrollCone, near Toledo, Ohio, assignorto Surface Combustion Corporation, Toledo, Ohio, a

corporation of Ohio v Application December 22, 1945, Serial No. 637,012

The present invention relates to the annealing of metal strip in coilsand has for its object to provide a furnace which shall be particularlywell adapted for annealing such material.

For a consideration of what I believe to be novel and my invention,attentign is directed to the following specification and the claimsappended thereto.

In the drawings- Fig. 1 is a vertical section through the improvedfurnace.

Fig. 2 is a vertical section on line 2-2 of Fig. 1.

Fig. 3 shows certain parts of Fig. 2 in a different operating position.

Fig. 4 is a plan view (with a portion broken away) of a spacer plateadapted to be positioned between the coils.

Fig. 5 is an enlarged fragmentary sectional view of the said spacerplate.

Fig. 6 is a plan view of an orifice plate adapte to be placed on top ofthe coil stack.

The improved furnace comprises a relatively tall heat insulatedbell-type cover or hood i adapted to be disposed over a stack 2 of coils3 of metal strip to be annealed, such as cold rolled steel strip, fiveof such coils being shown, the said hood and stack bein supp rted on afurnace base 4 above the floor level i by a structural steel workgenerally indicated at 6.

The hood i is a relatively light-weight affair comprised of an innermetal lining II, a layer of heat insulating material It and an outersteel casing it which gives rigidity to the hood. At the top of the hoodis a handle or fixture 8 by which the hood may be lifted by a crane. Theseat between the hood and furnace base is made gas-tight by a liquidholding trough l'l around the base for receiving a depending peripheralblade 20 carried by the hood.

The coils 3 are separated from each other by heat-conductingannularspacers 2i, each having a circumferential series of radially extendingopen-ended channels 22, so that the core 23 of the coil stack and theannular space 24 between the stack and hood are in open althoughrestricted communication by way of the said gas channels 22. On top ofthe coil stack there is placed a cover plate 25 having a relativelyrestricted central aperture 26 whereby to produce a back pressure in thecore 23 of the stack when a gaseous medium is introduced thereintothrough a central gas port 21 at the bottom of the stack. Consequently,exit of the gaseous medium from the core of the coil stack will beprimarily by way of the spacer channels 22 with resultant heat 4 Claims.(Cl. 233-42) exchange between the gaseous medium and the edges of thecoiled strip through the intermediary of the top and bottomwalls of thespacers. The use of channeled spacers between the coils does not per seconstitute part of the present invent on.

The primary object of the present invention is to provide improvementsin apparatus for the heating and cooling and forcible circulation of agaseous medium into and out of the space encompassed by the hood to theend that a given load of strip coils 3 may be processed more rapidlythan has heretofore been possible with conventional equipment.

In the present invention the central gas port 21 constitutes the upperend of an upcomer gas passage 30 in a sub-structure generally indicatedat II, the passage leading from a chamber 32 to which the gaseous mediumis delivered by a power-driven centrifugal fan 33 arranged in adowncomer g s pas age whose gas intake end is a gas port 34 at one sideof the foot of the coil stack 2 and whose lower or discharge end openson said chamber 32 as indicated at 38. To encompass the gas port 34 thehood i has a laterally extending bulge 36.

A plurality of hair-pin type combustion tubes 31 project into the saidchamber 32 from one end wall 38 thereof, each tube being fired by aburner-33'. The tubes are preferably arranged in laterally spaced setsof two tubes each, one tube above the other with their exhaustless 40adjacent each other and with their exhaust ends connected to a suctionexhaust manifold ii, the said sets of tubes being separated from eachother by vertical partition walls 42 which divide the chamber," in aplurality of parallelly extending'gas channels 43 for the said gaseousmedium. Transverse vertical bailies 44 may be provided in each of saidchannels to cause the gaseous medium to flow in a zig-zag course overthe tubes. Because the gases are heated after leaving said fan it willbe readily appreciated that the gases handled by the fan are relativelycool, thereby insuring the optimum operating efllciency of the fan.

After the completion of the heating operation, the gaseous medium whichis being circulated by the fan 33 must be cooled in order that the coils3 may be cooled with the least possible delay to below oxidizingtemperature before the hood I is removed. The fuel to the burners 30 is,of course, shut off but not the air, thereby insuring initial quickcooling of the tubes by air passing therethrough. Cooling of the saidgaseous me- 3 dium is accomplished by routing the same throughwater-cooled means comprising two radiators 50 and 5| located atopposite sides of the downcomer passage 3l35 wherein the fan ispositioned.

The water pipes leading to and from the radiators are indicated at 49.The radiator 50 is separated from said passage by a plate valve 53 andthe radiator 5| is separated from said passage by a similar plate valve54. The plate valve 53 is mounted on a horizontal shaft 55 to turntherewith and the valve plate 54 is mounted on a similar shaft 56 toturn therewith, the two shafts being interconnected by appropriategearing I! to turn in unison in opposite directions. When said platevalves are in upright position (as in Fig. 2) the return gaseous mediumflows directly to the fan but when they are in horizontal position (asin Fig. 3) the said medium must flow laterally as two streams to andthrough said radiators to reach the fan as will now be readilyunderstood. The downcomer duct has a vertical side wall 60 which has anorifice 6| coaxial with the fan to constitute the inlet to the fan.

It will be understood that the gaseous medium which is being circulatedby the fan will be of such composition as to provide a protectiveatmosphere for the metal strip which makes up the coils 3. A typicalgaseous mixture for this purpose will contain about 70.7% nitrogen,12.5% hydrogen, 10.5% carbon monoxide, 5% carbon dioxide, 0.5% methane,and 0.8% water vapor. Fresh gas to compensate for leakage and reductionin volume of the atmosphere on being cooled may be supplied to thecircuit at any suitable point as through an inlet 63 at the upper end 34of the downcomer gas passage.

A removable closure 64 in the end wall of chamber 32 permits readyaccess to the combustion tubes 31 for removal in case of repairs and aremovable closure 65 in the downcomer duct wall permits ready removal ofthe fan for inspection and repairs.

From the foregoing description it will be understood that there are nofuel supply pipes for burners or electric conductors for heatingelements leading to the hood or cover I and, therefore, there need be noloss of time in removing the hood from the furnace base at the end ofthe annealing cycle nor in starting the heating operation once the hoodhas been placed on the base. The use of cooling water for removing theheat of the charge during the cooling cycle permits a drastic reductionin the total length of the cycle, especially with large coils of thingauge material.

What I claim as new is:

1. A heat treating furnace comprising, in com-. bination, an enclosurefor the workto be treated and comprising a base whereon the work issupported, means forming an entrance passage for 4 the admission ofcirculated gas to said enclosure and means forming a return passage forthe withdrawal of the gas, a blower having an inlet connected to thereturn passage and having an outlet connected to the entrance passagefor circulating the gas to and from said enclosure, a tubular elementextending within said entrance passage with its inlet and outlet endstherewithout, means for producing a flow of cooling medium through thetube when the circulated gas is required to be cooled. and meanscomprising a burner at the inlet end of the tube for producing -a flowof hot gas through the tube when the circulated gas is required to beheated.

2. A furnace according to claim 1, wherein said return passage comprisesfirst and second flow paths leading to the blower, means for directingthe circulated gas through the first flow path when said gas requires tobe heated by said tube, and means in the second flow path for precoolingthe circulated gas before it reaches said tube.

3. A heat treating furnace comprising, in combination, an enclosure forthe work to be treated and comprising a base whereon the work issupported, means forming an entrance passage for the admission ofcirculated gas to said enclosure and means forming a return passage forthe withdrawal of the gas. a blower having an inlet connected to thereturn passage and having an outlet connected to the entrance passagefor circulating the gas to and from said enclosure, a tubular elementextending within said entrance passage with its inlet and outlet endstherewithout and with the inlet end open to the inflow of atmosphericair, means comprising a suction producing means coupled to the outletend of the tube to draw said air through the tube to cool the tube whenthe circulated gas is required to be cooled, and means comprising aburner at the inlet end of the tube for producing a flow of hot gasesthrough the tube when the circulated gas is required to be heated.

4. A furnace according to claim 3, comprising means in the returnpassage for precooling the air when it requires to be cooled by the tubein the entrance passage.

CARROLL CONE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date

